Liquid crystal display device

ABSTRACT

The leakage of light and the disclination occur at the ends of the pixel electrodes where the equipotential lines bend toward the pixel electrodes. A dielectric  207  having a high dielectric constant is provided at the ends of the pixel electrodes to lift up the equipotential lines toward the opposing electrode, in order to decrease the leakage of light and the disclination.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having a circuitconstituted by electric field effect transistors (FETs) such asthin-film transistors (TFTs) and to a method of fabricating the same.TFT stands for a semiconductor element including a semiconductor layer,a gate electrode, a source electrode and a drain electrode.

In this specification, an element substrate stands for a substrate, ingeneral. In which semiconductor elements are formed.

In this specification, a display device stands for a device, in general,which produces a bright/dark display relying upon changes in theelectric signals, and a device which produces a display by applyingelectric signals to the liquid crystals is called a liquid crystaldisplay device.

2. Description of the Related Art

In recent years, attention has been given to a technology forconstituting TFTs by using a thin semiconductor film (several nm toseveral hundred nm thick) formed on a substrate having an insulatingsurface. The TFT is widely applied to electronic devices such as ICs andsemiconductor devices, and it has been desired to develop the TFT as aswitching element particularly for the liquid crystal display devices.

Known liquid crystal display devices can be roughly divided into twotypes: i.e., those of the active matrix type and those of the passivematrix type. A liquid crystal display device of the active matrix typeuses TFTs as switching elements and is capable of displaying a highquality. The liquid crystal display device of the active matrix isusually used for the notebook-type personal computers, but it isexpected that it can also be used for household TVs and portableterminals.

Among the liquid crystal display devices of the active matrix type, theliquid crystal display device of the projection type is capable ofproducing a display of a large size by expanding the picture on ascreen. Concerning the liquid crystal display device of the projectiontype, technology has recently been developed to realize the portabledevices by decreasing the size of the optical system by designing theliquid crystal display panel in a small size. A decrease in the size ofthe optical system helps lower the cost of the optical system and,hence, makes it possible to cheaply provide a liquid crystal displaydevice.

The liquid crystal display device of the active matrix type is generallyreverse-drives the lines. Among the reverse-drives of the lines, thereverse-drive of the source lines is the one in which as shown in aschematic diagram of FIG. 21, the polarity of a signal voltage writteninto the pixel TFTs connected to the signal lines of m columns isdiffered for each of the neighboring signal lines. The polarities of thesignal voltages written into the pixel TFTs connected to the signallines are changed depending upon the frames of odd numbers (FIG. 21A)and the frames of even numbers (FIG. 21B). Upon alternatingly drivingthe liquid crystals by changing the polarities of the signal voltageswritten into the pixel TFTs, the liquid crystals are prevented frombeing printed. The reverse-drive of gate lines is executed by replacingthe signal lines of FIG. 21 by the scanning lines.

On the interface of the oriented film, the liquid crystals are sooriented as to lift up an end thereof. In this specification, adirection from an end close to the interface of the oriented film ofliquid crystal molecules toward an end lifted up from the oriented film,which is orthogonally projected onto the surface of the substrate, isreferred to as “pretilted direction”. Further, an angle subtended by theinterface of the oriented film and by the long axis of liquid crystalsnear the interface of the oriented film, is referred to as “pretiltedangle”. The pretilted angle is imparted by either the rubbing or theswitching of liquid crystals near the interface of the oriented film byapplying an electric field to the liquid crystals.

In this specification, further, the defective orientation that stemsfrom nearly the reversed pretilted direction of the adjacent liquidcrystals on the interface of the oriented film is referred to as“disclination”. Further, though the pretilted direction of the liquidcrystals is the same, there exists a region where the pretilted anglelocally differs due to the electric field distribution and the irregularrubbing. The defective orientation of liquid crystals that develop whenthe orientation is not normal turns out to be locally bright like theleakage of light when the two pieces of polarizer plates are arranged onthe liquid crystal panel. The orientation of liquid crystals in whichthe pretilted direction is the same but in which the pretitlted angle islocally different, is referred to as “leakage of light” in thisspecification.

When the liquid crystal display device is driven by the active matrixsystem, the quality of display is spoiled by the leakage of light anddisclination. That is, in the normally white mode, a light-shieldingfilm is necessary for concealing the leakage of light and thedisclination, and the numerical aperture drops.

In the liquid crystal display device in which fine pixels are formedsuch as the one of the projection type, the disclination and the leakageof light occur at a ratio which is no longer negligible relative to thepixels. Further, as the leakage of light and the disclination are notall concealed due to the deviation in the alignment of thelight-shielding film, the leakage of light like bright line and thedisclination are seen at the time of black display, and the contrastdrops. That is, in the liquid crystal display device of the projectiontype, what is important is how to suppress the leakage of light and thedisclination.

As compared to the smectic liquid crystals having a layered structureand a highly oriented order, the nematic liquid crystals tend to developthe disclination and the leakage of light due to an electric fieldestablished between a pixel electrode and another pixel electrode. Inthe orientation system using nematic liquid crystals, therefore, it isnecessary to take a countermeasure to lower the disclination and theleakage of light.

How the leakage of light and the disclination occur will now bedescribed with reference to FIG. 18 which is a sectional viewschematically illustrating the pixel portion of the liquid crystaldisplay device. Between the neighboring pixel electrodes in FIG. 18, itis now presumed that a first pixel electrode 101 a has a potential of +5V and a second pixel electrode 101 b has a potential of −5 V. Let it nowbe presumed that an opposing electrode 102 has a potential of 0 V. In aregion where the equipotential lines 103 are in parallel with thesurface of the pixel electrode, the liquid crystals of the positive typeare so oriented that the long axes of the liquid crystal molecules 108are perpendicular to the surface of the pixel electrode. The liquidcrystals of the positive type stand for the liquid crystals having apositive dielectric anisotropy. At the end of the pixel electrode,however, the equipotntial lines are bent, and the liquid crystalmolecules 106 are oriented aslant with respect to the surface of thepixel electrode, i.e., are defectively oriented. It is considered thathow to lower the bending of equipotential lines at the end of the pixelelectrode is important from the standpoint of lowering the defectiveorientation.

At an end of the pixel electrode, there exists a region 104 of leakageof light where the pretilted angle locally differs. Since theequipotential lines are bent at the end of the pixel electrode, theliquid crystal molecules 106 at the end of the pixel electrode cannot beso switched that the long axes thereof become perpendicular to thesurface of the pixel electrode.

Further, there exists a region where the pretilted direction of theliquid crystals becomes opposite to the pretilted direction determinedby the rubbing direction 107 due to the electric field established at anend of the pixel electrode. Then, the pretilted angle and the pretilteddirection locally change sharply on the interface of the oriented film,whereby the orientation of the liquid crystals is greatly distorted andthe disclination occurs in the region 105.

That is, the disclination and the leakage of light are caused as theequipotential lines that are in parallel with the surface of the pixelelectrode are bent at an end of the pixel electrode. In the inventiondescribed below, a structural contrivance is made so as to suppress thebending of equipotential lines as much as possible at the end of thepixel electrode.

SUMMARY OF THE INVENTION

It is an assignment of the present invention to provide an elementstructure which is capable of preventing the leakage of current and thedisclination in the liquid crystal display device of the active matrixtype.

In this specification, the height of a dielectric stands for a distancebetween the surface of the pixel electrode with which the dielectriccomes into contact and the uppermost end of the dielectric. In thisspecification, further, the cell gap stands for a distance between thesurface that comes in contact with the opposing electrode and thesurface that comes in contact with the main surface of the pixelelectrode. The main surface of the pixel electrode stands for a flatsurface that occupies not less than 30% and, preferably, not less than50% of the pixel electrode. That is, the main surface of the pixelelectrode stands for a flat surface that occupies a maximum area of thepixel electrode.

FIGS. 5A to 5C illustrate a principle of this invention. FIG. 5 is asectional view of a pixel portion in the liquid crystal display device.Referring to FIG. 5A, a first pixel electrode 901 a and a second pixelelectrode 901 b are provided on a flat surface. An opposing electrode902 is provided facing the pixel electrodes. At the end of the pixelelectrode, equipotential lines 903 are bent toward the pixel electrodecausing the occurrence of disclination and leakage of light.

Referring to FIG. 5B, a dielectric 904 of a high dielectric constant isformed on the ends of the pixel electrodes. With the dielectric 904 ofthe high dielectric constant and a dielectric of a low dielectricconstant, i.e., liquid crystals being connected in series at the ends ofthe pixel electrodes, a voltage is reluctantly applied to the dielectricof the high dielectric constant. With the dielectric 904 of the highdielectric constant being provided at the ends of the first pixelelectrode 901 a and of the second pixel electrode 901 b, the voltage isreluctantly applied to the dielectric of the high dielectric constant.Accordingly, the equipotential lines are lifted on the dielectric of thehigh dielectric constant toward the opposing electrode 902. That is,upon providing the dielectric of the high dielectric constant on theends of the pixel electrodes, there is produced an effect forsuppressing the equipotential lines from bending at the ends of thepixel electrodes. The components of equipotential lines in parallel withthe surface of the pixel electrode increase resulting in an increase inthe electric field component in a direction perpendicular to thesurfaces of the pixel electrodes.

Referring to FIG. 5C, when the height of the dielectric 904 is toogreat, the equipotential lines 903 swell conspicuously toward theopposing electrode 902, which is detrimental to orienting the liquidcrystals. Namely, there exists an optimum value concerning the height ofthe dielectric.

It is considered that the region where the disclination and the leakageof light occur is the region where the equipotential lines are bendingrelative to the surfaces of the pixel electrodes. Therefore, thedielectric of the high dielectric constant should be formed in theregion where the disclination and the leakage of light occur to suppressthe bending of equipotential lines.

FIG. 2 is a model of simulation illustrating, in cross section, thepixel portion of the liquid crystal display device, wherein the deviceis simulated by providing a dielectric 304 having a relative dielectricconstant of 30 on a first pixel electrode 303 a and on a second pixelelectrode 303 b. The dielectric has a height (h) of 0.5 μm and a width,in cross section, of 6.0 μm. The dielectric 304 is formed beingoverlapped on the first pixel electrode and on the second pixelelectrode over an equal width (L). The width (L) over which thedielectric 304 is overlapped on the first pixel electrode and on thesecond pixel electrode is 2.0 μm. The potential of the first pixelelectrode is +5 V, the potential of the second pixel electrode −5 V, andthe potential of the opposing electrode 301 is 0 V. A cell gap (d) is4.5 μm. The device is simulated by using physical values of ZLI4792(manufactured by Merc Co.) at room temperature. The ZLI4792 exhibits arelative dielectric constant of 8.3 in the direction of long axis and arelative dielectric constant of 3.1 in the direction of short axis. Therubbing directions 305 and 306 meet at right angles with each other. Theliquid crystals are levo-rotary twist oriented. The distance (s) is 2.0μm between the first pixel electrode 303 a and the second pixelelectrode 303 b. The pitch among the pixels is 18 μm. FIG. 3 shows theresults of simulation. The first pixel electrode, second pixel electrodeand opposing electrode are provided on a light-transmitting substrate.

Further, the structure without dielectric on the ends of the first pixelelectrode and the second pixel electrode was simulated by using thesimulation model of FIG. 19. The simulating conditions were the same asthose of the simulation model of FIG. 2 except that no dielectric wasused. The same elements as those of FIG. 2 are denoted by the samereference numerals. The simulated results are shown in FIG. 20.

According to the simulated results of FIG. 20, the orientation of liquidcrystals is shown by a two-dimensional cross section. There are shownequipotential lines, liquid crystal director and transmission factor.The transmission factor indicates the leakage of light from the end ofthe first pixel electrode in a width of 3.4 μm. It is further learnedthat there is a disclination of a width of 3.6 μm from the end of thesecond pixel electrode. The distance between the first pixel electrodeand the second pixel electrode is 2.0 μm and, hence, the sum (x) ofwidth of the leakage of light and the disclination is 9.0 μm.

According to the simulated results of FIG. 3 by providing the dielectricat the ends of the pixel electrodes, however, the equipotential linesare suppressed from being bent toward the pixel electrodes due to thedielectric of the high dielectric constant and, hence, the equipotentialline components increase in parallel with the surfaces of the pixelelectrodes. The sum (x) of widths of the disclination and the leakage oflight was 7.5 μm. The region where the disclination and the leakage oflight have occurred decreased by 16% as compared to FIG. 20.

When the simulated results of FIG. 3 are compared with the simulatedresults of FIG. 20, it is learned that the sum (x) of widths of thedisclination and the leakage of light is decreased by 1.5 μm due to theformation of the dielectric at the ends of the pixel electrodes, thedielectric having a dielectric constant larger than a dielectricconstant of liquid crystals in the direction of long axis. Since thepitch among the pixels is 18 μm, the region where the disclination andthe leakage of light occur is decreased by about 8% of the width of thepixel, and the numerical aperture can be improved.

The device was simulated in the simulation model of FIG. 2 by changingthe height (h) of the dielectric under the following five conditions.The cell gap (d), the width (L) over which the dielectric is overlappedon the first pixel electrode and the width (L) over which the dielectricis overlapped on the second pixel electrode, vary depending upon theconditions. The dielectric possessed a relative dielectric constant of30.

-   -   Condition (1): d=4.5 μm, L=1.0 μm    -   Condition (2): d=4.5 μm, L=2.0 μm    -   Condition (3): d=3.0 μm, L=1.0 μm    -   Condition (4): d=2.0 μm, L=0.2 μm

FIG. 4 shows a relationship between the height of the dielectric and thesum of widths of the disclination and the leakage of light, wherein theabscissa represents a ratio of the height of the dielectric to the cellgap, and the ordinate represents the sum of the widths of the leakage oflight and the disclination.

The condition (1) is compared below with the condition (2). That is,under the condition (1), the dielectric occupies a small proportion ofthe pixel electrode, and a small effect is exhibited for decreasing thedisclination and the leakage of light. Under the condition (2), thedielectric is formed so as to be overlapped on the pixel electrodes overa width 1.3 μm to 1.4 μm close to the end thereof from a position atwhere the disclination and the leakage of light would occur when thereis no dielectric. The disclination and the leakage of light aredecreased by a width of a maximum of 1.5 μm.

In driving the liquid crystal display device by applying a voltagethereto, a region where a black level of good quality is accomplished isthe one where the equipotential lines are nearly in parallel with thesurface of the pixel electrode. When the dielectric is provided on sucha region, the leakage of light and the disclination rather increase dueto the bending of the equipotential lines that stem from the contact ofthe dielectric having a different dielectric constant. Under thecondition (4), therefore, the dielectric is provided slightly (by 0.5μm) on the inside of a position where the disclination and the leakageof light would occur when there is no dielectric. As compared to whenthere is no dielectric, therefore, the disclination and the leakage oflight are decreased by a maximum of 0.5 μm.

When the conditions (2), (3) and (4) are compared with one another, itis learned that the disclination and the leakage of light are markedlydecreased by providing a dielectric of a high dielectric constant forthose liquid crystal display devices having larger cell gaps. It isfurther learned that when the height of the dielectric is too large, theequipotential lines are excessively swollen toward the opposingelectrode, and the disclination and the leakage of light ratherincrease.

The invention (1) is concerned with a liquid crystal display devicecomprising pixel electrodes, a dielectric overlapped on the ends of thepixel electrodes, an oriented film covering the pixel electrodes and thedielectric, and liquid crystals on the oriented film, the liquidcrystals having a positive dielectric anisotropy, and the dielectrichaving a relative dielectric constant larger than a relative dielectricconstant of the liquid crystals in the direction of long axis.

In the invention (2), the liquid crystals have a negative dielectricanisotropy, and the dielectric has a relative dielectric constant largerthan the relative dielectric constant of the liquid crystals in thedirection of short axis.

In both the invention (1) and the invention (2), the voltage is appliedin a divided manner to an insulator of liquid crystals having a lowdielectric constant in a circuit in which the insulator of liquidcrystals of the low dielectric constant and a dielectric of a highdielectric constant are connected in series and are held between thepixel electrodes and the opposing electrode. By providing the dielectricof the high dielectric constant at the ends of the pixel electrodes,therefore, the equipotential lines are lifted up toward the opposingelectrode. This suppresses the occurrence of the leakage of light andthe disclination caused by the bending of equipotential lines toward thepixel electrodes at the ends of the pixel electrodes. To obtain thisaction, the relative dielectric constant of the dielectric provided atthe ends of the pixel electrodes must be larger than the relativedielectric constant of the liquid crystals.

The invention (3) is concerned with a liquid crystal display devicecomprising pixel electrodes, a dielectric overlapped on the ends of thepixel electrodes, an oriented film covering the dielectric and the pixelelectrodes, and liquid crystals on the oriented film, the dielectrichaving a relative dielectric constant of not smaller than 20.

In the invention (3), it is desired that the dielectric has a relativedielectric constant which is not smaller than 20, so that the relativedielectric constant of the dielectric is larger than the relativedielectric constant of the liquid crystals as considered from a generaldielectric constant of the liquid crystals.

In the case of the nematic liquid crystals having a positive dielectricanisotropy, the relative dielectric constant of the liquid crystals inthe direction of long axis is usually from about 8 to about 20. In thecase of the liquid crystal display device using nematic liquid crystalshaving the positive dielectric anisotropy, therefore, it is consideredthat the relative dielectric constant of the dielectric needs be notsmaller than 20.

In the case of the nematic liquid crystals having a negative dielectricanisotropy, the relative dielectric constant of the liquid crystals inthe direction of short axis is usually from about 8 to about 20. In thecase of the liquid crystal display device using nematic liquid crystalshaving the negative dielectric anisotropy, therefore, it is consideredthat the relative dielectric constant of the dielectric needs be notsmaller than 20.

The invention (4) is concerned with a liquid crystal display devicecomprising pixel electrodes, a dielectric overlapped on the ends of thepixel electrodes, an oriented film covering the dielectric and the pixelelectrodes, and liquid crystals on the oriented film, the dielectrichaving a relative dielectric constant of not smaller than 30.

In the invention (4), the relative dielectric constant of the dielectricis selected to be 30 to observe the effect of greatly decreasing thedisclination and the leakage of light in the simulation by using themodel of FIG. 2. The higher the dielectric constant of the dielectric,the larger the effect for lifting up the, toward the opposing electrode,the equipotential lines that bend toward the pixel electrodes at theends of the pixel electrodes. Therefore, the effect for greatlydecreasing the disclination and the leakage of light is obtained evenwhen the dielectric has a relative dielectric constant which is largerthan 30.

The inventions (5) to (8) comprise pixel electrodes, an oriented film onthe pixel electrodes, a dielectric on the ends of the pixel electrodesand liquid crystals on the oriented film and on the dielectric, making adifference from the inventions (1) to (4). Even by forming the orientedfilm which is an insulator on the pixel electrodes and by forming thedielectric thereon, the equipotential lines can be lifted by thedielectric at the ends of the pixel electrodes toward the opposingelectrodes. In the liquid crystal display device using liquid crystalshaving a positive dielectric anisotropy, the relative dielectricconstant of the dielectric must be larger than the relative dielectricconstant of the liquid crystals in the direction of long axis, as amatter of course. In the liquid crystal display device using liquidcrystals having a negative dielectric anisotropy, the relativedielectric constant of the dielectric must be larger than the relativedielectric constant of the liquid crystals in the direction of shortaxis. The relative dielectric constant of the dielectric may be selectedto be not smaller than 20 considering from a general dielectric constantof the liquid crystals. As the effect is confirmed by simulation, therelative dielectric constant of the dielectric may be selected to be notsmaller than 30.

The invention (9) is concerned with the liquid crystal display device of(4) or (8), wherein the cell gap is not smaller than 2.0 μm but is notlarger than 4.5 μm, and the height of the dielectric is not larger than17% of the cell gap.

The invention (9) will now be described with reference to a graph ofFIG. 4. The leakage of light and the disclination decrease with anincrease in the height of the dielectric, become constant at a certainheight of the dielectric and, then, rather increase as the height of thedielectric further increases. In the liquid crystal display devicehaving the cell gap which is not smaller than 2.0 μm but is not largerthan 4.5 μm, the disclination and the leakage of light rather increaseas the dielectric becomes too high. When the height of the dielectric isnot larger than 17% of the cell gap, however, the leakage of light andthe disclination decrease monotonously with an increase in the height ofthe dielectric.

The invention (10) is concerned with a liquid crystal display device ofany one of (1) to (5), comprising an opposing electrode provided facingthe pixel electrodes, and an oriented film formed on the opposingelectrode, wherein a gap is maintained between the dielectric and theoriented film formed on the opposing electrode.

In this invention, the dielectric provided at the ends of the pixelelectrodes is different from a spacer that is provided for maintainingthe cell gap of the liquid crystal display device to be of apredetermined thickness.

The invention (11) is concerned with a liquid crystal display device ofany one of (1) to (8), wherein the dielectric is an oxide containingtitanium or tantalum. For example, a ditantalum pentoxide (Ta₂O₅) and atitanium dioxide (TiO₂) have relative dielectric constants of as high as30 or larger, and can be used as the dielectric of the invention.

The thus determined structure of the pixel portion of the invention isfor bringing the lines of electric force of when an electric field isapplied to be perpendicular to the flat surface on where the pixelelectrodes are formed, and can be widely used as means for decreasingthe defective orientation of liquid crystals in both the orientationsystem of the normally white mode and the orientation system of thenormally black mode.

If defective orientation of liquid crystals due to ruggedness is notinduced, this invention can be applied to the orientation system thatuses smectic liquid crystals. For example, the invention can be appliedto the liquid crystal display devices using ferroelectric liquidcrystals and anti-ferroelectric liquid crystals. The invention can befurther applied to a liquid crystal display device using a materialcured by adding liquid crystalline high molecules to the smectic liquidcrystals followed by the irradiation with light (e.g., ultravioletrays).

The constitution of the pixel portion of the invention can be widelyused as means for adjusting the electric field distribution in thedisplay device which optically modulates the dimmer layer by applying avoltage to the dimmer layer through the semiconductor elements.

In the liquid crystal display device of the projection type, inparticular, the leakage of light and the disclination are projected ontothe screen being enlarged through an optical system that uses lenses.Therefore, this invention is particularly effective in the liquidcrystal display device of the projection type.

The effect of the invention can be exhibited to a sufficient degree evenwhen there is formed an inorganic film having a function for preventingthe short-circuiting as an insulating film between the upper surfaces ofthe pixel electrodes and the oriented film. Presence of the dielectricon the ends of the pixel electrodes still makes it possible to preventthe equipotential lines from bending toward the pixel electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view (embodiment) illustrating a pixel portionof this invention;

FIG. 2 is a sectional view illustrating a model of simulation;

FIG. 3 is a sectional view illustrating the results of simulation ofwhen a dielectric is provided on the ends of pixel electrodes;

FIG. 4 is a diagram illustrating a relationship between the height ofthe dielectric and the sum of widths of the leakage of light and thedisclination;

FIGS. 5A to 5C are sectional views schematically illustrating theprinciple of this invention;

FIG. 6 is a top view (embodiment) illustrating the ends of the pixelelectrodes of this invention;

FIGS. 7A and 7B are sectional views (embodiments) illustrating the endsof the pixel electrodes of this invention;

FIGS. 8A and 8B are sectional views (embodiments) illustrating the endsof the pixel electrodes of this invention;

FIGS. 9A and 9B are views (embodiments) illustrating a pixel portion ofthis invention;

FIGS. 10A and 10B are views (embodiments) illustrating the pixel portionof this invention;

FIGS. 11A and 11B are top views (embodiment 1) illustrating the stepsfor fabricating an active matrix substrate;

FIGS. 12A and 12B are a top view and a sectional view (embodiment 2)illustrating a step for fabricating the active matrix substrate;

FIGS. 13A and 13B are a top view and a sectional view (embodiment 1)illustrating a step for fabricating the active matrix substrate;

FIG. 14 is a sectional view (embodiment 2) illustrating a liquid crystaldisplay device;

FIGS. 15A to 15F are perspective views (embodiment 3) illustratingexamples of electronic devices;

FIGS. 16A to 16D are views (embodiment 3) illustrating an example of anelectronic device;

FIGS. 17A to 17C are views (embodiment 3) illustrating examples ofelectronic devices;

FIG. 18 is a sectional view illustrating the disclination and theleakage of light;

FIG. 19 is a sectional view illustrating a model of simulation;

FIG. 20 is a sectional view illustrating the results of simulation ofliquid crystal orientation at the ends of the pixel electrodes; and

FIGS. 21A and 21B are top views illustrating the reverse-drive of thesource lines.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

In order to maintain a high numerical aperture in the pixel portions ofthe liquid crystal display device, it is a recommended method to form aninterlayer film on the scanning lines, on the signal lines and on thecapacitor electrodes, and to form the ends of the pixel electrodes beingoverlapped on the scanning lines, on the signal lines and on thecapacitor electrodes. In the top view illustrating the embodiment of theinvention, however, the scanning lines, signal lines and pixelelectrodes are drawn without being overlapped one upon the other foreasy comprehension of the positional relationship among thecharacteristic portions of the pixel electrodes, scanning lines andsignal lines. A recommended method of fabricating the liquid crystaldisplay device will be described later in detail by way of a workingexample.

FIG. 1 is a perspective view illustrating an embodiment of thisinvention. A dielectric 207 is provided on the ends of a first pixelelectrode 203 and a second pixel electrode 204. The dielectric 207 isprovided on the ends of a third pixel electrode 205 and a fourth pixelelectrode 206, as a matter of course.

FIG. 6 is a top view of the perspective view of FIG. 1. A chain lineA-A′ and a chain line B-B′ in the perspective view of FIG. 1 correspondto the positions of a chain line A-A′ and a chain line B-B′ in FIG. 6.The pixel portions in the top view of FIG. 6 represents a liquid crystaldisplay device which reverse-drives the gate lines. A dielectric film207 is formed on the ends of the first pixel electrode 203 and thesecond pixel electrode 204 along the scanning line 202. It is desiredthat the dielectric film has a relative dielectric constant of notsmaller than 20 or not smaller than 30. A signal line 201 is providedintersecting the scanning line. The third pixel electrode 205 isneighboring the first pixel electrode with the signal line sandwichedtherebetween. The fourth pixel electrode 206 is neighboring the secondpixel electrode with the signal line sandwiched therebetween.

In the liquid crystal display device which reverse-drives the gatelines, the pixel electrodes having potentials of polarities differentfrom each other are neighboring each other at the ends of the pixelelectrodes along the scanning lines. Therefore, an equipotential planeis subject to be bent toward the pixel electrodes. It is thereforedesired to provide the dielectric 207 on the ends of the pixelelectrodes along the scanning line to impart the action for lifting upthe equipotential plane at the ends of the pixel electrodes toward theopposing electrode.

The dielectric may or may not be provided on the ends of the first pixelelectrode 203 and the third pixel electrode 205 which are neighboringwith the signal line 201 sandwiched therebetween. The first pixelelectrode 203 and the third pixel electrode 205 are neighboringmaintaining potentials of the same polarity, and the equipotential linesare not so much bent at the ends of the first pixel electrode and thethird pixel electrode. Therefore, whether the dielectric be provided atthe end of the first pixel electrode 203 and at the end of the thirdpixel electrode 205 maintaining potentials of the same polarity, may bedetermined depending upon the degree of leakage of light that occurswhen there is no dielectric.

FIGS. 7A and 7B are sectional views of when the top view of FIG. 6 iscut along the chain line A-A′ and the chain line B-B′. FIG. 7Aillustrates a state where the first pixel electrode 203 is neighboringthe second pixel electrode 204 with the scanning line (not shown)sandwiched therebetween, and the dielectric 207 is formed on the ends ofthe first pixel electrode and the second pixel electrodes. FIG. 7Billustrates a state where the dielectric is not provided on the secondpixel electrode 204 and the fourth pixel electrode 206 which areneighboring each other with the signal line (not shown) sandwichedtherebetween.

In the liquid crystal display device which reverse-drives the sourcelines, the signal line 201 may be replaced by the scanning line, and thescanning line 202 may be replaced by the signal line in the top view ofFIG. 6.

As the dielectric, there may be used titanium dioxide (TiO₂).

The cross section of the dielectric of the invention needs not be of arectangular shape as shown in the sectional view of FIG. 7. As shown ina sectional view of FIG. 8A, for example, the dielectric 207 formed onthe ends of the pixel electrodes 208 may have a trapezoidal shape incross section. As shown in a sectional view of FIG. 8B, further, thedielectric 207 provided on the ends of the pixel electrodes 208 may havea mild arcuate shape in cross section. When the dielectric has arectangular shape in cross section, the tips of the hairs tend to bedisturbed at the time of rubbing, and the rubbing becomes irregular nearthe bottom of the dielectric that is in contact with the pixelelectrodes. The dielectric having a trapezoidal shape or an arcuateshape in cross section is effective in conducting the rubbing. When thedielectric is formed in the rectangular shape, the electric fieldbecomes discrete near the apex of rectangle of the dielectric, causing adefect in the arrangement of liquid crystals. It is therefore desired toform the dielectric in a trapezoidal shape or in an arcuate shape incross section to suppress the loss of uniformity in the distribution ofelectric field. Either the dielectric has the trapezoidal shape or thearcuate shape in cross section, the height (h) of the dielectric standsfor a distance between the surface of the pixel electrode in which thedielectric comes in contact and the uppermost end of the dielectric. Thewidth (L) of the dielectric stands for a distance from the end of thepixel electrode to a tangent between the side surface of the dielectricand the upper surface of the pixel electrode. That is, the width (L)stands for a width over which the dielectric is overlapped on the pixelelectrode. The disclination and the leakage of light are caused by thebending of the equipotential lines at the ends of the pixel electrodes.Therefore, the dielectric 207 that works to suppress the bending ofequipotential lines should exist on at least the ends of the pixelelectrodes 208 as shown in FIG. 8C.

In the liquid crystal display device which reverse-drives the lines in aperspective view of FIG. 9A, the first pixel electrode 203 and the thirdpixel electrode 205 have potentials of the same polarity, and the secondpixel electrode 204 and the fourth pixel electrode 206 have potentialsof a polarity different from that of the first pixel electrode 203. Thevicinity of apex of the first pixel electrode 203 is close to the secondpixel electrode 204 and the third pixel electrode 206 having potentialsof a polarity different from that of the first pixel electrode. At theapex of the first pixel electrode, therefore, the equipotential planegreatly bends toward the pixel electrode. It is therefore desired thatonly a portion of the dielectric 207 near the apex of the pixelelectrode is locally swollen toward the opposing substrate, thedielectric 207 being so formed as to be overlapped on both the end ofthe second pixel electrode 204 and the end of the first pixel electrode203 neighboring thereto maintaining a potential of a different polarity.This makes it possible to lower the leakage of highly bright light thatis seen near the apex of a rectangle of the pixel electrodes that arepatterned in a rectangular shape.

FIG. 9B is a sectional view of when the perspective view of FIG. 9A iscut along the chain line C-C′. The height of the dielectric 207 islocally increased at near the apexes of the fourth pixel electrode 205that is patterned in a rectangular shape.

In the liquid crystal display device which reverse-drives the lines in aperspective view of FIG. 10A, the first pixel electrode 203 and thethird pixel electrode 205 have potentials of the same polarity, and thesecond pixel electrode 204 and the fourth pixel electrode 206 havepotentials of a polarity different from that of the first pixelelectrode 203. In this case, the dielectrics 209 to 210 are so formed asto be overlapped on the ends of both the second pixel electrode and thefirst pixel electrode neighboring thereto maintaining a potential of adifferent polarity. Here, the dielectrics 209 provided near the apex ofthe pixel electrode have a relative dielectric constant larger than thatof the dielectric 210 lying therebetween. The dielectric having a higherrelative dielectric constant is more effective in lifting up theequipotential lines at the ends of the pixel electrodes toward theopposing electrode. By suitably selecting the relative dielectricconstant of the dielectric 209, therefore, it is allowed to prevent theleakage of highly bright light near the apex of the pixel electrode.

As for a method of changing the relative dielectric constant of thedielectric, it is allowable to use two kinds of films having dissimilarrelative dielectric constants as materials of the dielectric, or tochange the relative dielectric constant by changing the film-formingconditions while using the same material. In depositing the titaniumdioxide, the refractive index of the titanium dioxide film that isformed can be increased by lowering the oxygen pressure at the time ofdeposition (Optical Thin-Film, Kyoritsu Shuppan Co., p. 143). There is arelationship n²/c²=ε₀ε_(r)μamong the refractive index n₁, dielectricconstant ε₀ of vacuum, relative dielectric constant ε_(r) and magneticpermeability μ. Here, since the magnetic permeability μ remains nearlyconstant irrespective of the substances, the relative dielectricconstant εr of the film tends to increase with an increase in therefractive index (n) of the film that is deposited. By changing theoxygen pressure at the time of deposition, therefore, the refractiveindex changes, and a dielectric film having a different relativedielectric constant is formed.

FIG. 10B is a sectional view of when the perspective view of FIG. 10A iscut along a chain line D-D′. In providing the dielectric on the end ofthe third pixel electrode 205, the relative dielectric constant of thedielectrics 209 formed near the apexes of the pixel electrodes isselected to be higher than the relative dielectric constant of thedielectric 210 between the dielectrics 209.

Embodiment 1

An Embodiment 1 of the present invention will now be described withreference to FIGS. 11A to 13B.

First, an electrically conducting film is formed on a substrate 601having an insulating surface shown in a sectional view of FIG. 12B, andis patterned to form a scanning line 602. The scanning line also worksas a light-shielding film for protecting a semiconductor layer that willbe formed later from light. Here, a quartz substrate is used as asubstrate 601, and a laminated-layer structure of a polysilicon film (50nm thick) and a tungsten silicide (W-Si) film (100 nm thick) is used asthe scanning line 602. Further, the polysilicon film prevents thesubstrate from being contaminated with the tungsten silicide.

Next, an insulating film 603 is formed maintaining a thickness of 100 to1000 nm (typically, 300 to 500 nm) to cover the scanning line 602. Here,a silicon oxide film having a thickness of 100 nm formed by the CVDmethod and a silicon oxide film having a thickness of 280 nm formed bythe LPCVD method are laminated one upon the other.

Then, an amorphous semiconductor film is formed maintaining a thicknessof 10 to 100 nm. Here, the noncrystalline silicon film (amorphoussilicon film) is formed maintaining a thickness of 69 nm by the LPCVDmethod. Next, the noncrystalline silicon film (amorphous silicon film)is crystallized by a technology disclosed in Japanese Patent Laid-OpenNo. 78329/1996. According to the technology disclosed in thispublication, a metal element is selectively added to the noncrystallinesilicon film to promote the crystallization followed by the heattreatment to form a crystalline silicon film which spreads starting fromthe region where the metal element is added. Here, nickel is used as ametal element for promoting the crystallization and, then, a heattreatment (450° C., one hour) is executed for dehydrogenation, followedby another heat treatment (600° C., 12 hours) for crystallization.

Then, nickel is put to the gettering from the region where the activelayer of TFT is formed. The region of the active layer of TFT is coveredwith a mask (silicon oxide film), phosphorus (P) is added to a portionof the crystalline silicon film and is heat-treated (at 600° C. in anitrogen atmosphere for 12 hours).

Then, after the mask is removed, unnecessary portions of the crystallinesilicon film are removed by patterning to form semiconductor layers 604a and 604 b. The semiconductor layers 604 a and 604 b are the samesemiconductor layers 604. FIG. 11A is a top view of the pixel after thesemiconductor layer is formed. There are shown a scanning line 602 and asemiconductor layer 604.

Next, to form a holding capacity, a resist is formed, and a portion(region for forming the holding capacity) 604 b of the semiconductorlayer is doped with phosphorus.

Then, the resist is removed and an insulating film is formed to coverthe semiconductor layer. Then, to increase the capacity of the holdingcapacitor, a resist is formed, and the insulating film is removed fromthe region 604 b where the holding capacity is to be formed.

Then, an insulating film (gate-insulating film 605) is formed by thethermal oxidation. Due to this thermal oxidation, the gate-insulatingfilm finally acquires a thickness of 80 nm. On the region where theholding capacity is to be formed, there is formed an insulating filmhaving a thickness smaller than that of other regions. It is desiredthat the insulating film has a thickness of 40 to 50 nm on the regionwhere the holding capacity is to be formed.

Next, the channel doping is effected onto the whole surface orselectively to add p-type or n-type impurities at a low concentration tothe region that serves as the channel region of the TFT. The step ofthis channel doping is the one for controlling the threshold voltage ofthe TFT. Here, boron is added by the ion-doping method by excitingdiborane (B₂H₆) by plasma but without effecting the mass separation. Itis, of course, allowable to employ the ion plantation method byeffecting the mass separation.

Next, contact holes that reach the scanning lines are formed by etchingthe insulating film.

Then, an electrically conducting film is formed and is patterned to forma gate electrode 606 a and a capacitor wiring 606 b. Here, use is madeof a laminated-layer structure of a silicon film (150 nm thick) dopedwith phosphorus and a tungsten silicide film (150 nm thick). The holdingcapacitor is formed by parts of the capacitor wiring and of thesemiconductor layer with the insulating film 605 as a dielectric.

FIG. 11B is a top view of a pixel after the gate electrode and thecapacitor wiring are formed. The gate electrode 606 a is electricallyconductive to the scanning line 602 through a contact hole 801. A regionwhere the semiconductor layer 604 is overlapped on the capacitor wiring606 b via an insulating film works as the holding capacitor.

Then, by using the gate electrode and the capacitor wiring as masks,phosphorus is added at a low concentration in a self-aligned manner. Theconcentration of phosphorus in the region to where it is added at a lowconcentration, is adjusted to be from 1×10¹⁶ to 5×10¹⁸ atoms/cm³ and,typically, from 1×10¹⁶ to 5×10¹⁸ atoms/cm³.

Next, a resist is formed and phosphorus is added at a high concentrationby using the resist as a mask, thereby to form a region containingimpurities at a high concentration that serves as a source region or adrain region. The phosphorus concentration in the region of the highimpurity concentration is adjusted to be from 1×10²⁰ to 1×10²¹ atoms/cmand, typically, from 2×10²⁰ to 5×10²⁰ atoms/cm³. In the semiconductorlayer, a region overlapped on the gate electrode serves as a channelregion, and a region covered with a resist serves as an impurity regionof a low concentration and works as an LDD region. After the impuritiesare added, the resist is removed.

Though not diagramed, the region that becomes an n-channel TFT iscovered with a resist, and boron is added to form a source region or adrain region in order to form a p-channel TFT used for a drive circuitformed on the same substrate as the pixels.

Next, after the resist is removed, a passivation film 607 is formed tocover the gate electrode 606 a and the capacitor wiring 606 b. Here, asilicon oxide film is formed maintaining a thickness of 70 nm. Next, theheat treatment is effected to activate the n-type or p-type impuritiesadded into the semiconductor layer at their respective concentration.Here, the heat treatment is effected at 950° C. for 30 minutes.

Then, an interlayer insulating film 608 of an inorganic material isformed. In this Embodiment, a silicon oxynitride film is formedmaintaining a thickness of 800 nm.

Then, a contact hole is formed to reach the semiconductor layer, and anelectrode 610 and a signal line 609 are formed. In this Embodiment, theelectrode and the signal lines are formed of a laminated-layer film of afour-layer structure in which a Ti film is formed maintaining athickness of 60 nm, a TiN film is formed maintaining a thickness of 40nm, an aluminum film containing Si is formed maintaining a thickness of300 nm, and a TiN film is formed maintaining a thickness of 100 nm allby sputtering in a continuous manner.

FIG. 12A is a top view of the pixel after the electrode and the signallines are formed. The signal line 609 is electrically conductive to thesemiconductor layer 604 through the contact hole 802. The electrode 610is electrically conductive to the semiconductor layer 604 through thecontact hole 803. FIG. 12B is a sectional view of the pixel portionformed through the above steps.

Then, the hydrogenation treatment is effected at 350° C. for one hour.

Next, an interlayer-insulating film 612 of an organic resin material isformed as shown in a sectional view of FIG. 13B. Here, an acrylic resinfilm having a thickness of 1.0 μm is used. Thereafter, a light-shieldingelectrically conducting film is formed maintaining a thickness of 100 nmon the interlayer-insulating film to thereby form a light-shieldinglayer 613.

Next, an insulating film 614 is formed maintaining a thickness of 100nm. The insulating film forms a silicon oxynitride film of a thicknessof 100 nm to 300 nm.

Then, a contact hole (not shown) is formed to reach the electrode 610.Next, after a transparent electrically conducting film (an indium-tinoxide (ITO) film here) is formed maintaining a thickness of 100 nm,pixel electrodes are formed by patterning. The distance is 2.0 μmbetween the first pixel electrode 616 and the second pixel electrode617.

There can be formed a holding capacitor using the pixel electrode (e.g.,first pixel electrode 616) and the light-shielding film 613 aselectrodes, and the insulating film 614 as a dielectric.

Then, the TiO₂ film is formed by the electron beam vaporization method.The material to be vaporized is contained in a crucible. Thermoelectronsemitted from the filament in high degree of vacuum are accelerated by apredetermined voltage and impinge upon the material to be vaporized, andthe material to be vaporized is heated and vaporizes due to the kineticenergy. The vaporized particles condense on the substrate. Oxygen isintroduced as a reactive gas to trigger the oxidizing reaction. The TiO₂film is formed maintaining a thickness of 0.5 μm.

Then, a resist is formed, and the TiO₂ film is etched with an aqueoussolution of hydrogen fluoride (HF). The TiO₂ film is formed in a stripedshape so as to be overlapped on the end of the first pixel electrode 616and on the end of the second pixel electrode 617 over a width of 2.0 μm.The TiO₂ film has a width of 6.0 μm. A dielectric film 615 is formed onthe ends of the pixel electrodes by etching the TiO₂ film which is adielectric having a high dielectric constant.

FIG. 13A is a top view of the pixel portion after the dielectric film615 is formed. The electrode 610 is electrically conductive to the pixelelectrode (e.g., third pixel electrode 618) through the contact hole804. FIG. 13B is a sectional view of when the top view of FIG. 13A iscut along a chain line H-H′ and a chain line G-G′.

In this specification, the substrate fabricated through the above stepsis called active matrix substrate.

The active matrix substrate of this Embodiment can be used for theliquid crystal display device of the transmission type. When there isused, as a pixel electrode, an electrically conducting film having afunction of reflecting light instead of the transparent electricallyconducting film, the active matrix substrate of this Embodiment can beused for the liquid crystal display device of the reflection type.

Embodiment 2

This Embodiment deals with the steps for fabricating a liquid crystaldisplay device of the active matrix type using the active matrixsubstrate fabricated in Embodiment 1. The description refers to FIG. 14in which the same elements (first pixel electrode 616, second pixelelectrode 617) as those of FIGS. 13A and 13B are denoted by the samereference numerals as those of FIGS. 13A and 13B.

First, the active matrix substrate is obtained in accordance withEmbodiment 1.

Next, a transparent electrode 701 of a transparent electricallyconducting film is formed on a light-transmitting substrate 700. In thisEmbodiment, the thus constituted substrate is called opposing substrate.

Then, an oriented film 702 is formed on the active matrix substrate andon the opposing substrate, and is rubbed. The liquid crystal displaydevice fabricated according to this Embodiment is a panel of theprojection type having a diagonal size of from about 0.3 inches to about1 inch. In the panel of this kind, the pixels have a size of as small as10 μm to 20 μm, and the defect caused by spacers becomes no longernegligible. The liquid crystal display device of this Embodiment,therefore, uses no spacer.

The active matrix substrate on which the pixel portions and the drivecircuits are formed, is stuck to the opposing substrate with a sealingmember (not shown). The sealing member contains a filler, and the twopieces of substrates are stuck together maintaining a uniform gap due tothe filler. The cell gap between the pixel portions is 4.5 μm.

Thereafter, a liquid crystal material 703 is poured into between the twosubstrates, and is completely sealed with a sealing agent (not shown).The liquid crystal material 703 may be a known material. Thus, theliquid crystal display device of the active matrix type is completed asshown in FIG. 14. As required, further, the active matrix substrate orthe opposing substrate is divided into a desired shape. Further, apolarizer plate is suitably provided relying upon the known technology.An FPC is stuck, too, according to the known technology.

Referring to Embodiment 1 and the graph of FIG. 4 and by selecting theheight of the dielectric to be 0.5 μm, the relative dielectric constantof the dielectric to be 30 and the cell gap to be 4.5 μm, it isestimated that the sum of widths by which the leakage of light and thedisclination are decreased is 1.5 μm as compared with when there is nodielectric 615.

The thus fabricated liquid crystal display panel can be used as adisplay unit for a variety of electronic devices.

Embodiment 3

The liquid crystal display device formed by implementing an embodimenteither above-mentioned Embodiments 1 or 2 can be applied to variouselectro-optical equipments. Thus the present invention can be applied toall of the electronic equipments having these electro-optical devices asthe display portion.

The following can be given as Embodiments of the electronic equipment:video cameras; digital cameras; projectors; head mounted displays(goggle type display); car navigation systems; car stereo; personalcomputers, portable information terminals (such as mobile computers,portable telephones and electronic notebook). An example of these isshown in FIGS. 15A to 15F, 16A to 16D, and 17A to 17C.

FIG. 15A shows a personal computer, and it includes a main body 20(01,an image input section 2002, a display portion 2003, and a keyboard2004. The present invention is applicable to the display portion 2003.

FIG. 15B shows a video camera, and it includes a main body 2101, adisplay portion 2102, a voice input section 2103, operation switches2104, a battery 2105, and an image receiving section 2106. The presentinvention is applicable to the display portion 2102.

FIG. 15C shows a mobile computer, and it includes a main body 2201, acamera section 2202, an image receiving section 2203, operation switches2204, and a display portion 2205. The present invention is applicable tothe display portion 2205.

FIG. 15D shows a goggle type display, and it includes a main body 2301;a display portion 2302; and an arm section 2303. The present inventionis applicable to the display portion 2302.

FIG. 15E shows a player using a recording medium which records a program(hereinafter referred to as a recording medium), and it includes a mainbody 2401; a display portion 2402; a speaker section 2403; a recordingmedium 2404; and operation switches 2405. This player uses DVD (DigitalVersatile Disc), CD, etc. for the recording medium, and can be used formusic appreciation, film appreciation, games and Internet. The presentinvention is applicable to the display portion 2402.

FIG. 15F shows a digital camera, and it includes a main body 2501; adisplay portion 2502; a view finder 2503; operation switches 2504; andan image receiving section (not shown in the figure). The presentinvention can be applied to the display portion 2502.

FIG. 16A is a front-type projector, and it includes a projection device2601 and a screen 2602. The present invention is applicable to a liquidcrystal display device 2808 which comprises one of the projection device2601.

FIG. 16B is a rear-type projector, and it includes a main body 2701, aprojection device 2702, a mirror 2703, and a screen 2704. The presentinvention is applicable to a liquid crystal display device 2808 whichcomprises one of the projection device 2702.

FIG. 16C is a diagram showing an example of the structure of theprojection devices 2601, 2702 in FIGS. 16A and 16B. The projectiondevice 2601 or 2702 comprises a light source optical system 2801,mirrors 2802, 2804 to 2806, dichroic mirrors 2803, a prism 2807, liquidcrystal display devices 2808, phase difference plates 2809, and aprojection optical system 2810. The projection optical system 2810 iscomposed of an optical system including a projection lens. ThisEmbodiment shows an example of three-plate type but not particularlylimited thereto. For instance, the invention may be applied also to asingle plate type optical system. Further, in the light path indicatedby an arrow in FIG. 16C, an optical system such as an optical lens, afilm having a polarization function, a film for adjusting a phasedifference, and an IR film may be suitably provided by a person whocarries out the invention.

FIG. 16D is a diagram showing an example of the structure of the lightsource optical system 2801 in FIG. 16C. In this embodiment, the lightsource optical system 2801 comprises a reflector 2811, a light source2812, lens arrays 2813, 2814, a polarization conversion element 2815,and a condenser lens 2816. The light source optical system shown in FIG.16D is merely an example, and is not particularly limited to theillustrated structure. For example, a person who carries out theinvention is allowed to suitably add to the light source optical systeman optical system such as an optical lens, a film having a polarizationfunction, a film for adjusting a phase difference, and an IR film.

Note that a transmission electro-optical device is used as the projectorshown in FIGS. 16A to 16D, a reflection type electro-optical device isnot illustrated.

FIG. 17A is a portable telephone, and it includes a main body 2901, anaudio output section 2902, an audio input section 2903, a displayportion 2904, operation switches 2905, and an antenna 2906. The presentinvention can be applied to the display portion 2904.

FIG. 17B is a portable book (electronic book), and it includes a mainbody 3001, display portions 3002 and 3003, a recording medium 3004,operation switches 3005, and an antenna 3006. The present invention canbe applied to the display portions 3002 and 3003.

FIG. 17C is a display, and it includes a main body 3101, a support stand3102, and a display portion 3103. The present invention can be appliedto the display portion 3103. The display of the present invention isadvantageous for a large size screen in particular, and is advantageousfor a display equal to or greater than 10 inches (especially equal to orgreater than 30 inches) in diagonal.

The applicable range of the present invention is thus extremely wide,and it is possible to apply the present invention to electronicequipment in all fields. Further, the electronic equipment of Embodiment3 can be realized by using a constitution of any combination ofEmbodiments 1 and 2.

As described above, this invention provides a liquid crystal displaydevice which decreases the defective orientation of liquid crystals suchas disclination and leakage of light of when the black level isdisplayed, and which can be favorably watched maintaining a highcontrast.

The leakage of light and the disclination occur in the liquid crystaldisplay device at the ends of the pixel electrodes due to that theequipotential plane bends toward the pixel electrodes, establishing anelectric field in a direction inclined relative to the surfaces of thepixel electrodes and causing the liquid crystals to be oriented alongthe electric field in the inclined direction. Therefore, a dielectric ofa high dielectric constant is provided at the ends of the pixelelectrodes to set the equipotential plane to be in parallel with thesurfaces of the pixel electrodes, thereby to prevent the disclinationand the leakage of light of liquid crystals.

1. A liquid crystal display device comprising pixel electrodes, adielectric overlapped on the ends of the pixel electrodes, an orientedfilm covering the pixel electrodes and the dielectric, and liquidcrystals on the oriented film, the liquid crystals having a positivedielectric anisotropy, and the dielectric having a relative dielectricconstant larger than a relative dielectric constant of the liquidcrystals in the direction of long axis.
 2. A liquid crystal displaydevice comprising pixel electrodes, a dielectric overlapped on the endsof the pixel electrodes, an oriented film covering the dielectric andthe pixel electrodes, and liquid crystals on the oriented film, theliquid crystals having a negative dielectric anisotropy, and thedielectric having a relative dielectric constant larger than a relativedielectric constant of the liquid crystals in the direction of shortaxis. 3-4. (Canceled)
 5. A liquid crystal display device comprisingpixel electrodes, an oriented film on the pixel electrodes, a dielectricprovided on the ends of the pixel electrodes, and liquid crystals on theoriented film and on the dielectric, the liquid crystals-having apositive dielectric anisotropy, and the dielectric having a relativedielectric constant larger than a relative dielectric constant of theliquid crystals in the direction of long axis.
 6. A liquid crystaldisplay device comprising pixel electrodes, an oriented film on thepixel electrodes, a dielectric provided on the ends of the pixelelectrodes, and liquid crystals on the oriented film and on thedielectric, the liquid crystals having a negative dielectric anisotropy,and the dielectric having a relative dielectric constant larger than arelative dielectric constant of the liquid crystals in the direction ofshort axis. 7-8. (Canceled)
 9. A liquid crystal display device accordingto claim 1, wherein the cell gap is not larger than 4.5 μm, and theheight of the dielectric is not larger than 25% of the cell gap.
 10. Aliquid crystal display device according to claim 2, wherein the cell gapis not larger than 4.5 μm, and the height of the dielectric is notlarger than 25% of the cell gap.
 11. A liquid crystal display deviceaccording to claim 1 further comprising an opposing electrode providedfacing the pixel electrodes, and an oriented film formed on opposingelectrode, wherein a gap is maintained between the dielectric and theoriented film formed on the opposing electrode.
 12. A liquid crystaldisplay device according to claim 1 wherein the dielectric is an oxidecontaining titanium or tantalum.
 13. A liquid crystal display deviceaccording to claim 1 wherein said liquid crystal display device isincorporated into an electronic equipment selected from the groupconsisting of a video camera, a digital camera, a projector, a headmounted display, a car navigation system, a car stereo, a personalcomputer, and a portable information terminal.
 14. A liquid crystaldisplay device according to claim 2, further comprising an opposingelectrode provided facing the pixel electrodes, and an oriented filmformed on opposing electrode, wherein a gap is maintained between thedielectric and the oriented film formed on the opposing electrode.
 15. Aliquid crystal display device according to claim 5, further comprisingan opposing electrode provided facing the pixel electrodes, and anoriented film formed on opposing electrode, wherein a gap is maintainedbetween the dielectric and the oriented film formed on the opposingelectrode.
 16. A liquid crystal display device according to claim 6,further comprising an opposing electrode provided facing the pixelelectrodes, and an oriented film formed on opposing electrode, wherein agap is maintained between the dielectric and the oriented film formed onthe opposing electrode.
 17. A liquid crystal display device according toclaim 2, wherein the dielectric is an oxide containing titanium ortantalum.
 18. A liquid crystal display device according to claim 5,wherein the dielectric is an oxide containing titanium or tantalum. 19.A liquid crystal display device according to claim 6, wherein thedielectric is an oxide containing titanium or tantalum.
 20. A liquidcrystal display device according to claim 2, wherein said liquid crystaldisplay device is incorporated into an electronic equipment selectedfrom the group consisting of a video camera, a digital camera, aprojector, a head mounted display, a car navigation system, a carstereo, a personal computer, and a portable information terminal.
 21. Aliquid crystal display device according to claim 5, wherein said liquidcrystal display device is incorporated into an electronic equipmentselected from the group consisting of a video camera, a digital camera,a projector, a head mounted display, a car navigation system, a carstereo, a personal computer, and a portable information terminal.
 22. Aliquid crystal display device according to claim 6, wherein said liquidcrystal display device is incorporated into an electronic equipmentselected from the group consisting of a video camera, a digital camera,a projector, a head mounted display, a car navigation system, a carstereo, a personal computer, and a portable information terminal.